Strujanje uzrokovano vjetrom u stratificiranom fluidu: numeričko istraživanje i primjena na Tršćanski zaljev u uvjetima jake bure

This study investigates the circulation driven by a severe bora wind event in the Gulf of Trieste during the stratification season. A preliminary numerical analysis of the wind driven transport in the surface boundary layer is carried out for an idealized, laterally unbounded, shallow domain. Then, the simulations are focused on the Gulf of Trieste, using a realistic bathymetry and assuming stably stratified initial conditions. First, the model is driven by constant wind forcing, then qualitative and quantitative estimations of the dynamics of the basin are made reproducing the strong Bora event of the 25 June 2002. Numerical results show good agreement with in situ measurements and remotely sensed images. The relevance of coastal upwelling and its persistence are also assessed. The results prove that mixing and coastal upwelling (both wind-driven) govern the circulation of the basin. When bora starts blowing, buoyant surface water is moved by EKMAN transport offshore inducing a bottom onshore current. Simultaneously, wind driven stirring breaks the initial stable stratification. The surface offshore current generates a sea surface level setup on the northern boundary. When bora decreases, this surface tilt is no longer sustained, and a reversal of the circulation is observed in the upper layer. The sensitivity to the wind forcing is also discussed. All of these issues are crucial to environmental problems such as pollutant dispersion or anoxia phenomena in the bottom layers of the Gulf.U ovom se radu analizira strujanje u Tršćanskom zaljevu uzrokovano jakom burom u vertikalno stratificiranom slučaju. Preliminarna numerička analiza strujnog polja uzrokovanog vjetrom urađena je za idealizirani slučaj horizontalno neograničene domene. Zatim su numeričke simulacije primijenjene na Tršćanski zaljev upotrebivši realnu batimetriju i uz pretpostavku vertikalno stabilne stratifikacije. 25. lipnja 2002. godine najprije je primjenijen stacionaran vjetar, a zatim realistična situacija jake bure. Rezultati numeričke integracije pokazuju dobro slaganje s in situ i daljinskim mjerenjima. Posebna je pažnja poklonjena intenzitetu obalnog “upwellinga” i njegovoj postojanosti. Rezultati ukazuju da su vertikalno miješanje i “upwelling” odgovorni za strujanje u bazenu. Bura uzrokuje EKMANOV transport i odnosi slatku vodu prema sredini zaljeva, te uzrokuje formiranje pridnene struje ka obali. Istovremeno vertikalno miješanje slabi vertikalnu stabilnost vodenog stupca. Površinska struja od obale prema sredini zaljeva uzrokuje nagib razine mora od sjeverne obale ka jugu. Kada prestane bura nagib razine mora se više ne može održati i javlja se površinska struja suprotnog smjera. U ovom je radu također istraživana osjetljivost numeričkih rješenja na utjecaj vjetra. Ovi su procesi važni za širenje otpadnih tvari kao i za eventualnu pojavu anoksije u pridnenom sloju zaljeva

Weibullova distribucija bure i juga na sjevernom Jadranu

Wind data measured at three off-shore stations in the northern part of the Adriatic Sea were considered: the Coastal oceanographic station Piran buoy (COSP), the PALOMA tower (the Gulf of Trieste) and the A. ALTA platform (Venice). Annual wind roses for all stations and additional seasonal wind roses for COSP are presented. The Weibull distribution function was applied to wind speed frequency distribution for winds from all directions and separately for bora and sirocco winds. Wind speed frequency distributions for bora winds measured at COSP and PALOMA are bimodal. One peak of this distribution of speeds belongs to nocturnal land breezes and another to bora winds. The peak separation method based on the difference in potential temperature of the atmospheric boundary layer (ABL) between two land stations (Udine and Zagreb) enabled the successful separation of the peaks of bora and land breeze winds. The frequency distribution of the wind speeds changed to the usual unimodal distribution when only those episodes were considered in which the potential temperature of ABL above Udine is higher than that above Zagreb.Obrađeni su podaci na tri morske postaje na sjevernom Jadranu: oceanografskoj plutači Obalne oceanografske postaje Piran (COSP), tornju Paloma u Tršćanskom zaljevu i na platformi A.ALTA ispred Venecije. Predstavljene su godišnje ruže vjetrova za sve tri postaje i dodatno sezonske ruže vjetrova za COSP. Weibullova distribucijska funkcija bila je primijenjena na razdiobu čestine brzine vjetra za vjetrove iz svih smjerova i posebno za buru i sirocco. Razdioba čestina brzine vjetra izmjerenog na COSP i PALOMA iz smjerova bure pokazala se kao bimodalna. Jedan vrh u toj distribuciji pripada dnevno-noćnoj cirkulaciji zraka, a drugi buri. Uspješna metoda separacije vrhova temelji se na razlici u potencijalnoj temperaturi zraka u atmosferskom graničnom sloju (AGS) iznad Udina i Zagreba. Razdioba čestina brzine vjetra postaje unimodalna kada se promatraju samo one epizode vjetra kad je potencijalna temperatura AGS iznad Udina viša od potencijalne temperature iznad Zagreba

Numeričko modeliranje zimske cirkulacije u Tršćanskom zaljevu (sjeverni Jadran)

Numerical simulations of the winter circulation in and around the Gulf of Trieste are presented. The model, based on the architecture of the Princeton Ocean Model, gave reasonable results for circulation in the Gulf during the winter period, when the dominant bora wind is blowing. Three model runs with different initial and surface boundary conditions show that there is an outflow along the shallow northern coastline of the Gulf and over the surface of the major part of the area, and an inflow at depth in the central and southern parts of the Gulf. However, the variability of the temperature and salinity fields when vertical fluxes of heat and salinity are present cause a weak outflow in an area near the southern part of the Gulf, and make the general circulation pattern more complex.Prikazana je numerička simulacija zimske cirkulacije u Tršćanskom zaljevu i oko njega. ACOAST -1.2 model, baziran na “Princeton Ocean Model” i ugnježđujući se u model šireg područja, daje prihvatljive rezultate za cirkulaciju u zaljevu zimi, kada je bura dominantan vjetar. Tri numerička eksperimenta s različitim početnim i graničnim uvjetima pokazuju izlaženje vode u cijelom stupcu sjevernog plitkog dijela zaljeva i uz površinu većeg dijela otvorenih granica, te kompenzacijski ulaz u donjem sloju središnjeg i južnog dijela. Promjene u poljima temperature i slanosti povezane s vertikalnim protocima topline i soli definiraju ovu kompleksnu sliku cirkulacije

Opažanja u obalnom području u okviru ADRICOSM projekta: Tršćanski zaljev

In the framework of the ADRICOSM project, from October 2002 to September 2003, a coastal observing system network was set up in the Gulf of Trieste. During this period, 36 CTD cruises were performed over a grid of 19 stations. An accurate data acquisition and quality check protocol was implemented for data decimation and smoothing. However, data analysis showed that conductivity/ salinity spikes were recorded at the depth of the very sharp thermocline observed in summer 2003. The exceptionally high salinity waters and the marked thermocline observed in the Gulf of Trieste in spring and summer 2003 directed us to compare the distributions of the temperature and salinity fields observed during ADRICOSM cruises with the available climatological values of the Gulf of Trieste, in order to assess whether the data collected during this research deviated significantly from the climatology.U okviru projekta ADRICOSM, od listopada 2002. do rujna 2003. godine, provedeno je 36 krstarenja tijekom kojih se uzorkovalo CTD sondom na 19 postaja u Tršćanskom zaljevu. Posebna pažnja je posvećena kvaliteti podataka. Tijekom ljeta 2003. godine opaženi su nagli skokovi vrijednosti saliniteta i gustoće (tzv. “spikes”) u području izražene termokline. U proljeće i ljeto 2003. godine vrijednosti saliniteta bile su izrazito visoke. Polja temperature i saliniteta određena za to razdoblje uspoređena su s postojećim podacima ne bi li se utvrdilo koliko odstupaju od prosjeka

Initial spread of an effluent and the overturning length scale near an underwater source in the northern Adriatic

The rise of an effluent emerging from the diffusers of the submarine sewage outfall of a small town (15000 PE) is numerically simulated with a model of initial dilution

February 2003 marine atmospheric conditions and the bora over the northern Adriatic

A vinter oceanographic field experiment provided an opportunity to examine theatmospheric marine conditions over the northern Adriatic. Mean February winds are from a northeasterly direction over most of the Adriatic and a more northerly direction along the western coast..

Prof. dr. Jadran Faganeli - prejemnik Velike nagrade Miroslava Zeia za življenjsko delo na področju dejavnosti Nacionalnega inštituta za biologijo

Prof. dr. Jadran Faganeli je vrhunski raziskovalec biogeokemičnih procesov v morju, zaposlen na Morski biološki postaji Nacionalnega inštituta za biologijo v Piranu. Njegov znanstveni opus je izjemen, saj obsega 122 izvirnih in preglednih znanstvenih prispevkov, od katerih je velika večina objavljenih v revijah s faktorjem vpliva. Prof. dr. Faganeli slovi kot mednarodno uveljavljeni raziskovalec, ki povezuje tako raziskovalce po svetu kot tudi raziskovalna področja z multidisciplinarnimi biogeokemičnimi raziskavami, katerih spoznanja uporabljajo na različnih raziskovalnih področjih, kot npr. v morski ekologiji in limnologiji